Question

B) GIVE REASON FOR THE FOLLOWING. (M-05) a) Zinc is considered an element, while zinc sulphide is considered a compound
b) Atomic weight of an element is also termed relative atomic mass.
c) The valency of all metals is considered positive and non metal negative.
d) Certain elements exhibit more than one valency.
e) Nobel gases are highly unreactive.​

Answer 1

Answer:

1. ZINC IS THE PURE ELEMENT BECAUSE IT HAS NOT REACTED WITH ANY OF OTHER METAL OR NONMETAL. ZINC SULPHIDE IS A COMPOUND BECAUSE IT HAS REACTED WITH SULPHUR TO MAKE COMPOUND.
2. A relative atomic mass (also called atomic weight; symbol: Ar) is a measure of how heavy atoms are. It is the ratio of the average mass per atom of an element from a given sample to 1/12 the mass of a carbon-12 atom.

Answer 2

Answer:

a) Because Zinc is present in free state whereas zinc sulphide is bonded chemically, zinc is bonded with sulphur.

b) Relative mass: Relative mass is equal to the number of times an atom of an element is heavier than 1/12 the mass of an atom of carbon. Hence the atomic weight of an element is also termed relative atomic mass as it is in comparison with the mass of 1/12 the mass of a carbon atom.

c) the valency of all metals is +ve because all metals give their electrons to others to obtain stable form they usually have valency 1,2,3,4 ,,,,,, whereas non-metals are -ve because they borrow electrons the reason is due to lack of  1,2 or 3 electrons to obtain stable state.

d) Some elements show variable valency because of the different electronic configurations. An atom of an element can sometimes lose more electrons than are present in its valence shell i.e. loss from the penultimate shell and hence exhibit more than 1 or variable valency. ... This is termed variable valency.

e) Noble gasses are highly unreactive because  The atoms of noble gases already have complete outer shells, so they have no tendency to lose, gain, or share electrons.

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